The present invention is directed to apparatus and methods for producing a orientation-dependant radiation (ODR) source for use in systems employing such methods and apparatus. Specifically, the invention relates to an optical target for use with image metrology technology for precision spatial measurement and image-based motion analysis.
The invention relates to new technology that allows for 3-D motion capture using a single camera. Prior patents that generally disclose the basic concepts include U.S. Pat. Nos. 5,936,722; 5,936,723; and 6,384,908, and U.S. Patent Application Publication Nos. 2010/00046857; 2007/0280508; and 2004/0233461, which are all incorporated herein by reference in their entirety.
U.S. Pub. No. 2010/00046857 discloses a target constructed by applying artwork on the front and back of a transparent substrate, such as a glass or plastic plate. The target enables of six-degree of freedom location of an object by way of a single camera. The x and y location is determined by the position of a landmark that can be readily detected, even in an uncontrolled scene. Such a landmark is commonly called a robust landmark. The robust landmark can be a starburst in the center of the target, as in FIGS. 9-11 of U.S. Pub. No. 2010/00046857. The starburst may be black or white. The z location is determined by the spacing of the four circles (also referred to as secondary landmarks) from the center of the starburst, along with other data.
The target disclosed in U.S. Pub. No. 2010/00046857 is a three-layer structure of substrate, front artwork, and rear artwork. The regions that extend radially outward from the starburst and between the secondary landmarks (i.e., the regions labeled 311a-316b in FIGS. 9-11) are grating regions that produce moiré patterns. The moiré patterns are seen as light and dark fringes that change in response to changes in orientation of the target. Small rotations produce moiré-pattern displacements that are visible to the eye. With the out-of-plane rotations revealed by the moiré patterns, the system is able to determine the six degree of freedom (“6-DOF”) pose of the target from a single camera image.